@MiKa
Hi.
oki, in case i'll add some explanation.. I'll be busy for this week but you can simply use the serial gw example from MySensors for getting started, this should work. I didn't need to create a special board in arduino for this board, so if you're using it, you'll need to install&use the mattairtech SAMD21 board definition for the pin mapping.
https://github.com/mattairtech/ArduinoCore-samd
Hi @Siddharth-Velappan
The warmup time of the MH Z19b is 3 minutes. So 2 is probably fine, but you could probably do 3 just in case. Although 2 would save your more battery time.
Do you mind explaining your setup a bit more? I would love to do something similar but I do not know where to get started with the PIC microcontroller!